Exhaust gas purification device

Abstract

A substrate (11) includes an inflow-side cell (21), an outflow-side cell (22), and a porous, gas-permeable partition wall (23) that separates the inflow-side cell (21) and the outflow-side cell (22) from each other, and also includes a first catalyst portion (14) that is provided on a side of the partition wall (23) that faces the inflow-side cell (21) at least at a portion in upstream side in an exhaust gas flow direction, and a second catalyst portion (15) that is provided on a side of the partition wall that faces the outflow-side cell at least at a portion in downstream side. With respect to a pore volume of pores with a pore size of 10 to 18 μm, when a measured value of the pore volume in the first catalyst portion (14) and the partition wall (23) within a region where the first catalyst portion (14) is provided is defined as a first pore volume, and a measured value of the pore volume in the second catalyst portion (15) and the partition wall (23) within a region where the second catalyst portion (15) is provided is defined as a second pore volume, the first pore volume is greater than the second pore volume. A catalytically active component contained in the first catalyst portion (14) and a catalytically active component contained in the second catalyst portion (15) are of different types.

The invention claimed is: 
     
       1. An exhaust gas purification catalyst comprising:
 a substrate; and 
 a catalyst portion provided in the substrate, 
 the substrate including:
 an inflow-side cell including a space whose inflow-side in an exhaust gas flow direction is open and whose outflow-side is closed; 
 an outflow-side cell including a space whose inflow-side in the exhaust gas flow direction is closed and whose outflow-side is open; and 
 a porous partition wall that separates the inflow-side cell and the outflow-side cell from each other, and 
 
 the catalyst portion including:
 a first catalyst portion that is provided at least on a portion of a side of the partition wall that faces the inflow-side cell, the portion being located on an upstream side in the flow direction; and 
 a second catalyst portion that is provided at least on a portion of a side of the partition wall that faces the outflow-side cell, the portion being located on a downstream side in the flow direction, 
 
 wherein, with respect to a pore volume of pores with a pore size of 10 to 18 μm, a first pore volume is greater than a second pore volume, wherein the first pore volume is a measured value of the pore volume in the first catalyst portion and the partition wall within a region where the first catalyst portion is provided, and the second pore volume is a measured value of the pore volume in the second catalyst portion and the partition wall within a region where the second catalyst portion is provided, 
 both the first catalyst portion and the second catalyst portion contain a catalytically active component, and the catalytically active component contained in the first catalyst portion in the greatest amount differs from the catalytically active component contained in the second catalyst portion in the greatest amount, the catalytically active components contained in the first catalyst portion and the second catalyst portion are each at least one selected from a group consisting of Pt, Pd, and Rh, 
 the first catalyst portion is present mainly on the surface of the partition wall, and 
 in a region extending from a downstream end portion toward the upstream side in the exhaust gas flow direction by a length corresponding to 1/10 of a length L of the substrate, the second catalyst portion has a larger mass in a portion that is present inside the partition wall than in a portion that is present on the surface of the partition wall. 
 
     
     
       2. The exhaust gas purification catalyst as set forth in  claim 1 ,
 wherein, when the first pore volume is taken as 1, the second pore volume is 0.95 or less. 
 
     
     
       3. The exhaust gas purification catalyst as set forth in  claim 1 ,
 wherein the catalytically active component contained in the first catalyst portion is Pd, and 
 the catalytically active component contained in the second catalyst portion is Rh.